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arXiv · 2303.16020

The SAMI-Fornax Dwarfs Survey III: Evolution of [$\alpha$/Fe] in dwarfs, from Galaxy Clusters to the Local Group

J. Romero-Gómez·Reynier F. Peletier·J. A. L. Aguerri·Steffen Mieske·Nicholas Scott·Joss Bland-Hawthorn·Julia J. Bryant·Scott M. Croom·F. Sara Eftekhari·Jesús Falcón-Barroso·Michael Hilker·Glenn van de Ven·Aku Venhola
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Abstract

Using very deep, high spectral resolution data from the SAMI Integral Field Spectrograph we study the stellar population properties of a sample of dwarf galaxies in the Fornax Cluster, down to a stellar mass of $10^{7}$ M$_{\odot}$, which has never been done outside the Local Group. We use full spectral fitting to obtain stellar population parameters. Adding massive galaxies from the ATLAS$^{3D}$ project, which we re-analysed, and the satellite galaxies of the Milky Way, we obtained a galaxy sample that covers the stellar mass range $10^{4}$ to $10^{12} M_{\odot}$. Using this large range we find that the mass - metallicity relation is not linear. We also find that the [$\alpha$/Fe]-stellar mass relation of the full sample shows a U-shape, with a minimum in [$\alpha$/Fe] for masses between $10^{9}-10^{10} M_{\odot}$. The relation between [$\alpha$/Fe] and stellar mass can be understood in the following way: When the faintest galaxies enter the cluster environment, a rapid burst of star formation is induced, after which the gas content is blown away by various quenching mechanisms. This fast star formation causes high [$\alpha$/Fe] values, like in the Galactic halo. More massive galaxies will manage to keep their gas longer and form several bursts of star formation, with lower [$\alpha$/Fe] as a result. For massive galaxies, stellar populations are regulated by internal processes, leading to [$\alpha$/Fe] increasing with mass. We confirm this model by showing that [$\alpha$/Fe] correlates with clustercentric distance in three nearby clusters, and also in the halo of the Milky Way.

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J. Romero-Gómez, Reynier F. Peletier, J. A. L. Aguerri, Steffen Mieske, Nicholas Scott, Joss Bland-Hawthorn, Julia J. Bryant, Scott M. Croom, F. Sara Eftekhari, Jesús Falcón-Barroso, Michael Hilker, Glenn van de Ven, Aku Venhola. 2023-03-28. The SAMI-Fornax Dwarfs Survey III: Evolution of [$\alpha$/Fe] in dwarfs, from Galaxy Clusters to the Local Group. https://doi.org/10.1093/mnras%2Fstad953

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